`Amazing' Discovery In The Sound

Startling Changes Found In Organism Populations May Mean That Excess Nitrogen Is Changing The Sound's Ecology.

June 10, 2000|By STEVE GRANT; Courant Staff Writer

Scientists have troubling new information that populations of one-celled organisms in Long Island Sound are changing radically, suggesting that the sudden die-off of lobsters and other species in the Sound may be symptomatic of a broader problem.

The new research found that increases and decreases in populations of species collectively known as foraminifera were closely related to increases in sewage treatment plant discharges, long blamed for excess nitrogen in the Sound.

The deaths of lobsters in the Sound have been traced to a paramoeba, but many scientists say other factors, including pollution, may have made the lobsters vulnerable.

Water quality engineers have known since the mid-1980s that excess nitrogen from treatment plants causes algae blooms that, in parts of the western Sound, lead to a condition called hypoxia, in which the water is so stripped of oxygen that many kinds of marine life must flee or die. But the new study suggests the nitrogen could be permanently altering the species composition of the Sound, though the scientists cautioned that more research is needed before any conclusions can be drawn.

The changes among foraminifera appear to have accelerated between 1996 and 1999, when the last samples were taken, according to Ellen Thomas, a micropaleontologist at Wesleyan University in Middletown involved in the research.

The foraminifera population``is changing very dramatically over a short period of time,'' she said. . ``It is really amazing.''

The research found that populations of one foraminifera species, Elphidium excavatum clavatum, crashed in the western end of the Sound, while another species, Ammonia beccarii, which likely is either able to withstand pollution or actually prefers such conditions, is now flourishing..

That suggests that increases in nitrogen and phosphorus discharges into the Sound, already blamed for damaging algae blooms, are affecting creatures at the bottom of the food chain.

Thomas and her husband, Joop Varekamp, a Wesleyan geochemist, are longtime researchers who have done extensive studies of marshes bordering the Sound. The latest work, about to be published with a series of new scientific papers on the Sound, was supported by the U.S. Geological Survey and Connecticut Sea Grant.

Thomas compared samples of foraminifera gathered in 1996 and 1999 with published data on samples collected in 1948 and 1961. Foraminifera are tiny protozoans, with shells containing calcium, that form part of the marine food chain.

In the oldest samples, Elphidium excavatum clavatum was dominant throughout the Sound, while Ammonia beccarii constituted only 2 or 3 percent of the population in a few samples. By 1996, however, Ammonia beccarii, the species that seems to endure or flourish in nitrogen pollution, had become dominant in the western Sound, which has the most severe pollution. Its populations remain small in most of the eastern Sound, which is much cleaner.

Excessive nitrogen and phosphorus discharges, blamed mostly on sewage treatment plant effluent, are a known problem that has prompted a major effort to reduce nitrogen in the Sound. It is expected to cost about $1 billion to improve sewage treatment plants in New York and Connecticut over the next 10 to 15 years -- not counting other costs for upgrading, rebuilding or expanding those plants.

But the new research suggests that the effects of the nitrogen problem may have been worsening and changing the ecology of the western Sound, which long has had the most serious pollution problems.

``If there are problems with oxygen supply for organisms at the bottom of the food chain, then it seems predictable the problems are there for other creatures in the same place,'' Thomas said.

The possible link between the increase in Ammonia beccarii and increased sewage became apparent by identifying a bacterial spore in sediment samples that is present in the guts of mammals and is not destroyed in their digestive tracts or in the sewage treatment process.

That work, conducted by Marilyn R. Buchholtz ten Brink, a research geochemist at the U.S.G.S. Woods Hole Field Center in Massachusetts, found evidence of increased sewage discharges in the western Sound in a pattern that paralleled the abundance of Ammonia beccarii.

While the research suggests a strong link between the change in foraminifera species and increased sewage, it is not proven, though it could help regulatory agencies make decisions, Buchholtz ten Brink said.

``It's going to take some additional study to determine exactly which factors are causing the foraminifera to change over decades,'' said Harley Knebel, a marine geologist at the Woods Hole center. Knebel is the overall editor of the collection of scientific papers that will include Thomas' research findings.

In related research, Varekamp found that mercury levels also are highest in the western portion of the Sound -- and appear to be affected more by sewage treatment plant discharges than previously thought.

Robert L. Smith, chief of the state Department of Environmental Protection's water management bureau, said the new research demonstrated that the state must move ahead with its plans for more advanced sewage treatment processes.

``We perceive the need to proceed with our plans to reduce nitrogen and restore the Sound back to a condition much closer to its natural condition,'' he said.